Why df and Finder shows different available disk space?

In home directory, df -h $HOME shows Filesystem Size Used Avail Use% Mounted on /dev/disk1 231G 177G 54G 77% / But in finder Any ideas? **EDIT** Attached df -h output /dev/disk1 231G 177G 54G 77% / # this is memory disk /dev/disk2 7.0G 677M 6.4G 10% /Users/HOME/Library/Caches # this is an encrypted dmg /dev/disk3s2 9.3G 7.0G 2.3G 76% /Volumes/NOT_HOME # this is a bindfs /Volumes/NOT_HOME/xxxx 9.3G 7.0G 2.3G 76% /Users/HOME/Library/some-folder